In one aspect, the invention relates to a fluid catalyst unit. In another aspect, the invention relates to improving the standpipe seal in a fluid catalyst unit. In a further aspect, the invention related to an improved fluid catalytic cracking process.
The bulk density of a fluid catalyst is an important characteristic which has a large influence on the fluidizability of the catalyst. Many newer fluid catalytic cracking catalysts, for example, have a higher bulk density than older catalysts. For example, several years ago, fluid catalytic cracking catalysts having bulk densities in the range of 0.75 to 0.85 were common. Today, some fluid catalytic cracking catalysts exhibit bulk density in the range of from above 0.85 to above 0.95 g/cc, a bulk density increase in many instances in excess of 10 percent. Old equipment designed for circulation of the older, lower bulk density catalysts may encounter problems when an attempt is made to switch over to newer style, higher bulk density catalysts. However, the newer cracking catalysts are generally desirable because they provide advantages in product selectivity, attrition resistance and longer half-life. An apparatus to provide good circulation of new high bulk density cracking catalyst would clearly be very desirable, especially where old style cracking units could be retrofitted. A process to overcome difficulties in circulating high bulk density fluid cracking catalysts would also be desirable.